bugc: add function inlining pass (inline transform, L2)#230
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Adds InliningStep (level 2, first — after L1 fold, before CSE/TCO/ JumpOpt) that replaces calls to eligible internal functions with a copy of the callee body spliced into the caller. Every inlined instruction is annotated transform:["inline"] via addTransform, and the body is bracketed by a virtual invoke (jump:true, identity, no target — the #213 optional-target signal) / virtual return, so a debugger can reconstruct a virtual activation. This lights up `inline` in the tracer, completing the transform set. v1 eligibility (correctness over coverage; follow-ups noted): - internal, non-recursive, single-return, LEAF callee; - applied at all call sites; callee deleted once fully inlined; - NOT inlined into self-recursive / TCO'd callers: inlining a helper into a tail-recursive call's arguments rewrites count(succ(n)) -> count(n+1), which the tail-call optimizer mishandles (pre-existing bug, tracked separately). Guarding this keeps the tailcall demos pristine. Return values use dest-substitution (not a continuation phi), which is robust to L3 block-merging; deep clones use structuredClone to preserve bigint const values. Updates optimizer-contexts tests: leaf helpers (add/dbl/addThree) now inline at L2+ (no real caller JUMP; inline activation instead), while recursive/multi-return functions (fact, isEven/isOdd, count) are untouched. Deferred to follow-ups: non-leaf/nested callees, multi-return, size-threshold (non-leaf) inlining.
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gnidan
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Jul 3, 2026
…hip) (#233) Amend the invoke spec's "Reconstructing activations" section to resolve an ambiguity #230's inline pass exposed: an inlined body's invoke/return markers must bracket the body (invoke on the first instruction, return on the last), never duplicate across interior instructions. Duplicated boundary markers push/pop spurious activations. - State the push/pop display semantics: invoke opens inclusive of its instruction, return closes after its instruction. - Require bracketed emission; permit the single-instruction body (entry==exit) to carry both invoke and return, processed push-then-pop. - Separate the two concerns explicitly: push/pop determines an activation's lifetime; membership determines which open activation an instruction belongs to. An activation stays open across non-member (interleaved caller) instructions. No schema change.
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Adds the function inlining pass and lights up
inlinein the tracer — completing the transform set (fold/tailcall/coalesce/inline). Emits per #229's frozen contract via the sharedaddTransformhelper.What it does
InliningStep(level 2, first — after L1 fold, before CSE/TCO/JumpOpt) replaces calls to eligible internal functions with a copy of the callee body spliced into the caller (α-rename, param→arg substitution, return→continuation via dest-substitution, callee deleted once fully inlined). Emission:jump:true, identity, notarget— the format: make invoke.target optional for internal calls #213 optional-target signal) on the first inlined instruction;transform:["inline"]on every body instruction (per-instruction membership, reorder-robust);arguments/dataomitted in v1 (per contract).v1 scope (correctness over coverage — follow-ups noted)
Eligible callee = internal, non-recursive, single-return, leaf; applied at all call sites.
count(succ(n))→count(n+1), which the tail-call optimizer mishandles (a pre-existing bugc bug — reproduces with inlining disabled; tracked separately). This guard keeps the tailcall demos pristine.Correctness notes
structuredClone(preservesbigintconst values).Test changes
inlining.test.ts: leaf single-return + multiple-sites correct at all levels with inline markers; TCO-protection (succ not inlined into count; count stays correct + tailcall).optimizer-contexts.test.ts: leaf helpers (add/dbl/addThree) now inline at L2+ (no real caller JUMP → inline activation); recursive/multi-return functions (fact, isEven/isOdd, count/succ) untouched.Verification
yarn build+ full bugc suite green (420 passed, 22 pre-existing skips).functionCallAndReturn(add) → inlined + correct;mutualRecursion→ untouched;count(succ)→ not inlined, tailcall intact, correct.